*3.1.7. Use of adjuvant*

Adjuvants are substances that are added in the vaccine to increase the bioavailability of vaccine. In the poultry sector, the oral route of vaccination is followed for most of the vaccines. The oral route of vaccine delivery is difficult due to barriers in the gastrointestinal tract. In order to overcome this challenge, the antigen must be protected from such an environment and the immune response must be activated. This challenge can be overcome by the use of adjutants. Adjuvants improve the safety of the vaccine and have a potential effect on inducing mucosal immune response [30]. The use of adjuvants provides good results for live vaccines. The adjuvants enhance the availability of vaccine and act as a sticking agent for vaccine and the mucous membranes of the body.

#### *3.1.8. Use of stabilizers*

Stabilizers are substances which are added in a vaccine to increase the shelf life of the vaccine. The stabilizers like Vac-Safe (Intervet), Vital Blue, etc. can be used for oral live vaccines like ND, IBD, IB, etc. of poultry. The skimmed milk at the rate of 2 g/L can also be added as a suitable alternative stabilizer [31].
